Currently, in the manufacture of optical discs, the retention of the discs during processing is performed typically by supporting devices essentially consisting of a rest plate, usually of circular form, on the upper surface of which supporting elements are mounted with each of the supporting elements being arranged so as to receive an optical disc. These supporting devices further include a suction assembly, generally consisting of a vacuum pump adapted to generate a vacuum region, connected to the individual supporting elements by respective sealed ducts.
In these current supporting devices, several different ducts are required for performing loading and unloading of the optical disc onto and from the supporting elements at different processing stations. As a result thereof, the simultaneous availability both of free optical discs adapted to be picked up from the rest plate and of optical discs firmly fixed to the rest plate for processing is essential.
In order to solve the above problem, a distribution valve has been interposed between the vacuum pump and the different ducts. This distribution valve of such prior supporting devices is used to attempt to ensure effectuation of the above operations as required, which involves considerable planning. Difficulties in planning this distribution device are further increased by the requirement that the rest plate must be capable of rotating, while the suction pump is integral with the supporting device's bearing structure.
For the purpose of promoting a correct positioning of the optical disc, the shape of the supporting elements in the supporting device substantially matches that of the received optical disc.
In addition, a supporting element base is provided with openings that, through the ducts, bring the vacuum region into communication with the optical disc surface turned towards the rest plate. These openings are positioned such that the openings are covered by the optical disc when the optical disc is placed on top of the supporting element. At this time, a pumping action generates a pressure difference between the interior and exterior of the supporting device so that the optical disc is tightly fixed against the supporting element, thereby preventing air from entering the above-mentioned openings.
Typically, the rest plate is rotated to bring the various supporting elements close to the different processing or handling work stations so that displacement of the optical discs out of their fixed seatings during the handling operations of the assembly are avoided.
However, since the securing openings of the optical disc are rather small, generation of a high pressure difference between the interior and exterior of the supporting device is required in order to ensure a sufficient force so as to retain the disc. As a result, suction pumps of relatively high power are necessary and a sealing tightness is to be ensured between the various components and/or ducts in which the vacuum is to be maintained. At the same time, however, the rest plate must be capable of movement.
Consequently, it has been found that the supporting device for optical discs described above has drawbacks associated with its complex structure. In particular, since this device is usually associated with a UV-ray station for drying a lacquer previously coated on the optical disc, it is necessary that a further cooling assembly be provided which is capable of cooling the optical disc during its exposure to radiation to thereby avoid overheating of both the optical disc and the components of the drying station.
To achieve this necessary cooling, the prior supporting device includes a further air pump capable of blowing air through appropriate channel lines placed both inside and outside the rest plate for reaching and thereby cooling the optical disc close to its center and at certain areas of its periphery.